Good point. You will see that 'Duftwolke' was bred 1956, but introduced 1963. Most sources give 1963/64 as the year of introduction. A period of 7 years between breeding and actual introduction is not unusual for commercial roses: It takes a couple of years to find out if the rose is worthwhile, then 1-2 years to propagate enough plants for the introduction. In the case of 'Prima Ballerina' we only have the year of introduction as 1957, even though it says "Bred 1957". I imagine this rose was actually bred around 1950, but we have no sources which would corroborate that.
What is somewhat surprising is the pollen parent 'Montezuma', which was introduced 1955. This is actually too short a time before 1956 for it to have been the parent of 'Duftwolke'. As 'Montezuma' participated at the Geneva trials in 1955, it must have been around already in 1953. It seems that Tantau got hold of the plant at an even earlier date. Maybe took some pollen at one of Swim's trial beds?